A Wyandanch man contacted his victims using a cellphone app and then robbed them of an expensive watch and a diamond ring, Suffolk County police said Tuesday.

Tyriek Coleman, 30, of Washington Avenue, used the app Letgo three times between May 13 and May 29 as he made off with merchandise worth $8,000, police said.

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He is charged with robbery, attempted robbery and criminal possession of stolen property. He is scheduled to be arraigned Tuesday at First District Court in Central Islip.

On May 13, Coleman contacted a seller of a men’s Breitling watch valued at $5,000, police said. When he met the seller, a man, Coleman discharged pepper spray in his face and fled with the watch.

On May 23, he met with a man selling a diamond ring, valued at $3,000, police said. He “used deception to steal the ring and flee,” police said. A spokeswoman Tuesday had no more details on Coleman’s deceptive tactics.

On Sunday, he met with another seller of a Breitling watch, worth $12,500, and used pepper spray again in an attempt to take the watch. The victim resisted, and Coleman fled empty-handed.

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Police said their investigation is continuing. Anyone with information about other incidents involving Coleman can contact the First Squad at 631-854-8152.